1. Field of Invention
The present invention relates generally to testing systems for evaluating musculoskeletal conditions of the human body. More particularly, the invention relates to an improved system for determining various characteristics of a patient's spine during muscular exertion against dynamic or isometric resistance.
2. Description of Related Art
In the field of exercise physiology, there are a number of different types of resistance to muscular exertion. One category is isometric resistance, which involves attempted motion against a stationary object. During isometric exercise, muscle fibers remain at a constant length.
Isometric resistance has been utilized in the past to analyze the human body. Examples of currently available products that utilize isometric resistance are the ISTU manufactured by Ergometrics Inc. and the Arcon ST by Applied Rehabilitation Concepts. While these systems have been useful for some purposes, they suffer a number of disadvantages.
In particular, testing systems which employ isometric resistance are unable to evaluate certain types of injuries, such as the injuries where a patient only experiences pain during actual movement of an affected body part. Moreover, since isometric systems are static, they are unable to accurately project a patient's actual dynamic lifting capacity. It is well known in the art that the strength of a particular body part varies depending upon the positioning of that body part. Testing systems that employ isometric resistance typically provide a limited number of exercise positions. Therefore, these systems are insufficient to accurately determine a patient's dynamic lifting capacity. Furthermore, since isometric systems do not involve any muscular movement of the patient, these systems lack the capacity to accurately evaluate muscular endurance.
An alternate means for resisting muscular exertion, in contrast to isometric resistance, is dynamic resistance. Dynamic resistance is resistance permitting actual movement of an object by a person exerting force against it. Dynamic resistance involves the shortening and lengthening of the person's muscle fibers. Today it is generally understood that there are three basic types of dynamic resistance: isotonic, isokinetic, and isodynamic.
Isotonic resistance involves the use of gravity or the simulation of gravity to resist muscular exertion. Some examples of exercise equipment utilizing isotonic resistance include free weights such as barbells, as well as Universal brand weight lifting machines. While gravity remains constant, the resistance to a specific muscle in this type of lifting exercise varies during the movement, due to changes in the angle of the lift.
Muscle movement against isotonic resistance occurs in two categories. First, the contractile phase involves shortening the muscle fibers while the weight is moved against gravity, or in other words "lifting" the weight. Second, the eccentric phase refers to motion wherein the muscle fibers are lengthened while the weight is moved in the same direction as the force of gravity, or in other words "lowering" the weight. Although isotonic resistance involves muscle activity in both the contractile phase and the eccentric phase, some exercises utilize what is known as "passive" resistance, wherein a all of a patient's motion is conducted against a counteractive force so that there is no eccentric phase of the exercise.
Exercise machines that provide isotonic resistance by using resistance other than weights are well known in the art. For example, a hydraulic source used to supply isotonic resistance is disclosed in U.S. Pat. No. 4,865,315 to Paterson et al, entitled "Dedicated Microprocessor Controlled Exercise Resistance Machine." In addition to hydraulic sources, isotonic resistance has been provided by pneumatic sources, as illustrated in U.S. Pat. No. 4,257,593 to Keiser, entitled "Pneumatic Exercising Device".
In contrast with isotonic resistance, isokinetic resistance, as now understood, restricts motion to a generally constant velocity, irrespective of the amount of force applied by the patient. Exercise machines that provide isokinetic resistance are well known in the art, and have used a number of different means for resistance. For example, systems are known that provide adjustable isokinetic resistance with mechanical or electric braking devices. Additionally, hydraulic sources have been used to provide isokinetic resistance. An example of an exercise machine that provides isokinetic resistance is the Liftask brand system, which is sold by Lumex Industries. Another example of an apparatus that provides isokinetic resistance to exercise is the Biodex dynamometer sold by Biodex Corp. of Shirley, N.Y. The Biodex machine provides isokinetic resistance for use in quantifying flexion and extension of a patient's lower spine.
Exercise machines that provide isokinetic resistance have been sufficient for some purposes. Specifically, users of exercise or testing machines that utilize passive isokinetic resistance have enjoyed a substantial degree of safety, since they are free to exert as much or as little force against the resistance as they wish without increasing their rate of motion. Furthermore, isokinetic resistance is beneficial since it can be used to determine a patient's strong and weak points in a particular exercise.
In contrast with isotonic and isokinetic resistance, isodynamic resistance, also called isoinertal resistance, provides a constant force or maximum torque during exercise, thereby allowing for changes in acceleration and velocity of motion in proportion to the muscular effort of the user. Although isodynamic devices were also referred to as "isokinetic" during the early 1980's, a distinction between the two has recently been recognized by the industry.
Isodynamic resistance has been useful in a number of applications, and is considered reasonably similar to "real world" lifting conditions, in that velocity changes are permitted to occur. In addition, exercise against passive isodynamic resistance can be conducive to safety since passive isodynamic resistance does not involve muscle movement in an eccentric phase.
Exercise machines providing isodynamic resistance are known in the art. For example, U.S. Pat. No. 4,733,859 to Kock et al, entitled "Exercise Apparatus" utilizes isodynamic resistance in conjunction with neck or foot exercise. Moreover, isodynamic systems have been used to obtain measurements, such as the velocity of the force displaced and the torque on an exercising joint, to evaluate a patient's level of impairment or to evaluate a patient's recovery.
Machines that utilize the various types of isometric and dynamic resistance in exercise or rehabilitation of the spine are well known today. One example of an apparatus that exercises the lumbar and lower thoracic regions of the spine is the Biodex back dynamometer, of Biodex Corp. of Shirley, N.Y. The Biodex back machine provides isokinetic resistance for use in quantifying flexion and extension of a patient's lower spine. Although the Biodex back apparatus is adequate for a number of uses, it has a number of limitations when considered for other purposes. In particular, the only type of dynamic resistance this machine is capable of supplying is isokinetic resistance. Furthermore, the Biodex machine only tests flexion and extension movements of the spine. Accordingly, the Biodex machine cannot facilitate simultaneous multi-axial spinal exercise.
Another example of a machine that utilizes various types of isometric and dynamic resistance in exercise or rehabilitation of the lumbar and lower thoracic regions of the spine is described in U.S. Pat. No. 4,637,607 to McArthur entitled "Drive Unit for Exercising Apparatus". The McArthur device facilitates forward flexion-extension and rotation of the spine. Although the McArthur device is useful in some applications, it is limited for other purposes since it cannot accommodate lateral bending movements and since it does not permit simultaneous multi-axial spinal motion.
Another example of an apparatus that exercises the lumbar and lower thoracic regions of the spine is sold by Isotechnologies, Inc. under the name "Isostation B-200". In contrast to the Biodex dynamometer, the B-200 apparatus supplies passive isodynamic resistance and isometric resistance against rotation, flexion-extension, and lateral bending of the lower spine.
Although the B-200 machine provides a number of benefits to its users, it has several limitations. For example, the B-200 device only facilitates isometric testing in a standing position. However, it is known in the art that such a position does not accurately represent the posture of maximum isometric strength or even a normal lifting posture. The B-200 is also limited because it does not facilitate isokinetic resistance.
Furthermore, although the B-200 machine provides a lateral bending axis that is coincident with the patient's spinal axis for such movement, the B-200 machine suffers a disadvantage in that its axes for forward flexion-extension and rotation are not coaxial with the patient's spine. Specifically, the forward flexion-extension and rotation axes of the B-200 apparatus are located about two to three inches posterior to the spine. Therefore, when the B-200 machine is used to conduct forward flexion-extension or rotation tests with a patient, the results are not as accurate as might be desired since the patient's spine does not coincide with the patient's axes of rotation and forward flexion-extension during the exercise. Accordingly, an improved dynamometer for the lower spine is needed to facilitate rotation and forward flexion-extension exercises about axes that are truly coincident with the spine.
A further limitation of the B-200 machine is that the structure of the apparatus prematurely limits the range of spinal extension. Accordingly, it would be beneficial to have a spinal dynamometer that permits a full range of spinal extension during exercise.
Another limitation of the B-200 machine in some applications is that it cannot properly isolate forward flexion movements of the lower back. Specifically, the patient's torso is harnessed to the B-200 device utilizing an assembly that is slidable linearly during flexion and extension exercises. As a result, the muscles of the lumbar as well the dorsal spine are engaged during such exercise. Therefore, if isolation of the muscles of the lumbar spine is desired during flexion and extension, B-200 machine might be inadequate.
Another disadvantage of the B-200 apparatus is that it does not provide a differential torque setting for the opposing movements of forward flexion and extension. In other words, the B-200 apparatus provides the same resistance for abdominal flexion movements as it does for lumbar extension movements. Typically, a patient's strength in abdominal flexion exercises is generally only 60% of the patient's strength in lumbar extension motions. Therefore, if the patient desires to use a substantial resistance during lumbar exercise, the patient might find the B-200 machine unsatisfactory, since the patient might not be able to overcome such a high level of resistance during the abdominal flexion portion of the exercise.
Another shortcoming of the B-200 machine is that it is not as safe as might be desired since the mass distribution and mechanical configuration of the machine generates a high moment of inertia when a patient engages in high speed exercises against low resistance. As a result, it is conceivable that the machine might swing beyond the patient's range of motion and cause injury. Accordingly, it would be advantageous to have a spinal dynamometer whose structure provides a mechanism for controlling inertia during rotational exercise, especially against lower levels of resistance.
A further disadvantage of the B-200 system is that it does not fully brace the patient's thorax during exercise, and therefore can result in spinal motion that is not properly restricted to the lumbar region of the spine. Moreover, the thoracic bracing provided by the B-200 is often uncomfortable for female patients. Another disadvantage is that the B-200 apparatus does not adequately prevent pelvic movement, especially during rotation exercise. This shortcoming is especially apparent when the B-200 apparatus is used by overweight people. Accordingly, it would be of benefit to have a spinal dynamometer that comfortably and effectively braces an exercising patient's thorax and pelvis to properly restrict to the lower spine area.
In contrast to the above-described machines that exercise the lower region of the spine, there are a number of machines that concentrate on exercising or rehabilitating the cervical or "neck" area of the spine.
One example is U.S. Pat. No. 4,733,859 to Kock et al, entitled "Exercise Apparatus." Kock et al seek to provide an apparatus for exercising the neck muscles, and provide independently adjustable isodynamic resistance against motion about forward flexion-extension, lateral bending, and rotation
Another example is disclosed in U.S. Pat. No. 4,768,779 to Oehman, Jr. et al, entitled "Back Exercise Apparatus with a Neck Exercise Attachment." A similar apparatus is shown in U.S. Pat. No. 4,893,808 to Mcintyre et al, entitled "Exercise Apparatus for the Neck." The Oehman, Jr. and Mcintyre machines facilitate neck exercise against adjustable dynamic or isometric resistance about one forward flexion-extension axis, one lateral bending axis, and/or one rotation axis. These machines additionally supply data to facilitate the computerized determination of parameters associated with the exercise, such as angular position, velocity, and torque.
Although the above-mentioned neck exercising machines have been satisfactory for some purposes, they suffer from a common limitation. In particular, the prior neck exercise machines do not account for the non-uniform movement characteristics of the cervical vertebrae and head.
The cervical region of the spine is a complex joint structure. During exercise, the ranges of motion of the various cervical vertebrae are non-uniform. Forward flexion and extension of the neck, for example, is achieved by a complex bending of the cervical vertebra including arching of the first vertebral articulation (the "atlas-axis") as well as flexing of the C2-C7 vertebrae. Lateral bending of the cervical spine similarly requires compound bending of the cervical vertebrae.
Thus, machines that only permit forward flexion-extension or lateral bending about a single axis are sometimes inadequate since they do not facilitate the natural motion of the neck and head. Further, machines that restrict forward flexion-extension or lateral bending to a single axis have limited usefulness in neck testing since they cannot discriminate between the activity of the head and the cervical spine.
Therefore, since the prior neck exercise arrangements discussed above only facilitate forward flexion and/or lateral bending of the cervical spine about a single axis for each exercise, these machines are not as useful as might be desired.